// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

// See net/disk_cache/disk_cache.h for the public interface of the cache.

#ifndef NET_DISK_CACHE_BLOCKFILE_MAPPED_FILE_H_
#define NET_DISK_CACHE_BLOCKFILE_MAPPED_FILE_H_

#include <stddef.h>

#include "base/macros.h"
#include "net/base/net_export.h"
#include "net/disk_cache/blockfile/file.h"
#include "net/disk_cache/blockfile/file_block.h"

namespace base {
class FilePath;
}

namespace disk_cache {

// This class implements a memory mapped file used to access block-files. The
// idea is that the header and bitmap will be memory mapped all the time, and
// the actual data for the blocks will be access asynchronously (most of the
// time).
class NET_EXPORT_PRIVATE MappedFile : public File {
public:
    MappedFile()
        : File(true)
        , init_(false)
    {
    }

    // Performs object initialization. name is the file to use, and size is the
    // amount of data to memory map from the file. If size is 0, the whole file
    // will be mapped in memory.
    void* Init(const base::FilePath& name, size_t size);

    void* buffer() const
    {
        return buffer_;
    }

    // Loads or stores a given block from the backing file (synchronously).
    bool Load(const FileBlock* block);
    bool Store(const FileBlock* block);

    // Flush the memory-mapped section to disk (synchronously).
    void Flush();

    // Heats up the file system cache and make sure the file is fully
    // readable (synchronously).
    bool Preload();

private:
    ~MappedFile() override;

    bool init_;
#if defined(OS_WIN)
    HANDLE section_;
#endif
    void* buffer_; // Address of the memory mapped buffer.
    size_t view_size_; // Size of the memory pointed by buffer_.
#if defined(POSIX_AVOID_MMAP)
    void* snapshot_; // Copy of the buffer taken when it was last flushed.
#endif

    DISALLOW_COPY_AND_ASSIGN(MappedFile);
};

// Helper class for calling Flush() on exit from the current scope.
class ScopedFlush {
public:
    explicit ScopedFlush(MappedFile* file)
        : file_(file)
    {
    }
    ~ScopedFlush()
    {
        file_->Flush();
    }

private:
    MappedFile* file_;
};

} // namespace disk_cache

#endif // NET_DISK_CACHE_BLOCKFILE_MAPPED_FILE_H_
